Compute partial derivative of density wrt. pressure
function dddp_pTX input Modelica.SIunits.AbsolutePressure p "Pressure"; input Modelica.SIunits.Temperature T "Temperature"; input Modelica.SIunits.MassFraction X[:] "Mass fractions"; output Real dddp(unit = "kg/(m3.Pa)"); end dddp_pTX;